// write your code here
import java.util.Scanner;


//斐波那契数列问题求和
public class Main{
    
    static long[] arr = new long[81];  //这里用long类型
    static{
        arr[0] = 0;
        arr[1] = 1;
        for(int i = 2; i < 81; i++){
            arr[i] = arr[i-1] + arr[i-2];
        }
    }
    
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        while(sc.hasNext()){
            int start = sc.nextInt();
            int from = sc.nextInt();
            long sum = 0;  //这里用long类型
            for(int i = start; i <= from; i ++){
                sum += arr[i];
            }
            System.out.println(sum);
        }
        sc.close();
    }
    
   
    
}